A wireless communications system generally refers to any telecommunications system which enables a wireless communication between the users and the network. In mobile communications systems users are capable of moving within the service area of the system. A typical mobile communications system is a Public Land Mobile Network (PLMN).
At present, third generation (3G) mobile systems, such as Universal Mobile Communication System (UMTS) and Future Public Land Mobile Telecommunication System (FPLMTS) later renamed as IMT-2000 (International Mobile Telecommunication 2000), are being developed. The UMTS is being standardized in the ETSI (European Telecommunication Standards Institute) whereas the ITU (International Telecommunication Union) is defining the IMT-2000 system. A radio interface is likely to be based on a wideband CDMA (Code Division Multiple Access) scheme, and therefore the third generation systems are often referred to as Wideband CDMA systems (WCDMA).
It has been suggested that future 3G systems should support multiple, simultaneous and independent calls to/from a single mobile station.
A problem with the prior publications related to 3G systems is that the handling of multiple calls is only specified on a “should-be possible” level. In other words, the prior publications almost completely ignore the management details of multicalls to/from a single mobile station. In a second generation (2G) system, such as the GSM (the Global System for Mobile communication), there is one situation where a mobile station can have two calls. Such a situation may arise if a subscriber has a supplementary service (SS) called Call Hold (CH). However, a 2G mobile station does not have multiple independently-controlled bearers (i.e. traffic channels), and in a CH situation, only one call can be active while all others are put on hold. Even in the so-called high-speed data transfer (HSCSD), a mobile station uses several time slots but all the time slots are assigned to a common traffic channel.